1. Field of the Invention
This invention relates to liquid, neutral one package coagulating agents for coagulating lacquers and coating compositions.
2. Statement of the Prior Art
In the application of lacquers, waxes or similar coating materials containing water insoluble organic substances, for example in the automotive industry, it is not possible to apply all of the materials to the parts to be coated. It is particularly in the lacquering of motor vehicles that there is an accumulation of overspray in the lacquer spray cubicles, which is removed from the spray cubicles by means of a water curtain and flushed into a settling tank. In order not to disturb the operation of the water carrying pipe, jet and sprinkler systems, (for example by tacky lacquer particles) and to remove from the circulating water the ingredients taken up, chemicals have to be added to the water to coagulate the substances in question. In this connection, the separation of the sprayed lacquer particles taken up by the water and their agglomeration to a dischargeable coagulate preferably should take place in one and the same operation.
Depending on the industrial installations used, a lacquer coagulant is employed whereby either the lacquer coagulate floats in the settling tank enabling it to be skimmed off the surface of the water, or the coagulate sediments and is subsequently scraped off the bottom of the tank by means of a scraper belt.
In order to obtain coagulation, i.e. separation of the lacquer particles and their agglomeration to form a dischargeable coagulate, alkaline powdered and alkaline liquid products and also powdered neutral products have hitherto been added to the circulating water. A liquid two step coagulating agent may also be introduced through an elaborate metering system.
Thus, British Patent Application No. 1,512,022 describes flocculating agents, i.e. agents which cause particles to combine with one another under the effect of intermolecular, bridge forming macromolecules. Agents such as these are made up of inorganic metal salts acting as clarifying agents, such as ferrous chloride or aluminium sulfate, and organic cationic polymers, such as polyvinyl pyridine or polyamines in aqueous solution.
Water soluble cationic polymers which are obtainable in powder form and used as flocculating agents are described in German Patent Application No. 27 49 295. To improve flocculation behavior and, at the same time, to reduce the molecular weight of the polymer and hence to increase the solubility of the product, powdered water soluble inorganic salts are added. This results in the formation of a water soluble cationic polymer in the form of a solid mass.
However, the use of powdered coagulating agents of this type is attended by the serious disadvantage that they have first to be suspended in water for the coagulation process. This presents problems in addition to the metering of the agents. Moreover, the stirring operation which is required for thorough suspension of the powder form products has an adverse effect upon the desirable flocculation process essential to the invention. This in turn adversely affects the mode of action and necessitates the use of relatively high concentrations of coagulating agent. In addition, the use of coagulating agents in powder form is not possible any place where dust emission has to be strictly avoided.
The pH values of the aqueous solutions of the coagulating agents previously normally used are generally in the alkaline range. This ensures that separation of the individual lacquer or wax particles is generally adequate and the operation of the water carrying systems is not disturbed. However, this necessitates careful monitoring of the alkalinity of the baths and, in some cases, neutralization of the coagulate waters before discharge into the drainage system.
Due to the alkalinity or the increased pH value of the baths, the resins or binders present in the lacquers can be hydrolyzed. Troublesome foaming is the result and relatively expensive antifoam agents additionally have to be introduced.